1. Field of the Invention
This invention relates to dental restorations and methods of manufacture thereof. In particular, this invention relates to splints, laminates, veneers, and dental bridges comprising glass fiber reinforcement, wherein the reinforcing glass fibers have been heat treated to prevent fraying and separation of the fibers.
2. Brief Discussion of the Prior Art
Fiber-reinforced composites have found increasing use in the field of materials for dental restorations, and are described, for example, in U.S. Pat. Nos. 4,717,341 and 4,894,012 to Goldberg et al., as well as U.S. Pat. No. 4,107,845 to Lee, Jr. et al. Fiber-reinforced composites generally comprise at least two components, a polymeric matrix and fibers embedded within the matrix. The composite materials may further comprise a filler material. Common polymeric matrices include those known for use in composite dental materials, for example polyamides, polyesters, acrylates, polyolefins, polyimides, polyarylates, polyurethanes, vinyl esters, or epoxy-based materials. Other polymeric matrices include styrenes, styrene acrylonitriles, ABS polymers, polysulfones, polyacetals, polycarbonates, polyphenylene sulfides, and the like. The fibers used to reinforce composite material may comprise glass, carbon, or polymer fibers such as polyaramide and polyethylene, as well as other natural and synthetic fibers.
Fiber-reinforced composite materials provide several advantages, most notably increased strength and stiffness. As described in U.S. Pat. Nos. 4,717,341 and 4,894,012 to Goldberg et al., such materials may be used as structural components in a variety of dental appliances, taking the form of bars, wires, beams, posts, clasps, and laminates. The fibers preferably take the form of long, continuous filaments, although the filaments may be as short as 3 to 4 millimeters. Where the composites take the form of elongated wires, the fibers are at least partially aligned and oriented along the longitudinal dimensions of the wire. However, depending on the end use of the composite material, the fibers may also be otherwise oriented, including being normal or perpendicular to that dimension. These structural components are used in traditional bridges, crowns, artificial teeth, dentures, implants, veneers, as well as in connection with orthodontic retainers, space maintainers, splints, and the like.
A bridge, in particular, is a device for the restoration and replacement of one or more natural teeth, replacing at least one missing tooth and supported on either side by the remaining (abutment) teeth. A bridge generally comprises a pontic for replacement of the missing tooth, and a connector which connects the pontic to a retaining member, such as a crown formed on an abutment tooth adjacent the pontic. By their nature, bridges must be aesthetic, as well as strong, in order to withstand forces generated by chewing and to maintain the positions of the abutting teeth. A number of bridge designs disclosed in the prior art are intended to either enhance strength or ease of preparation. For example, U.S. Pat. No. 5,074,791 discloses a bridge comprising a pre-formed pontic, which simplifies preparation. The so-called xe2x80x9cwinged bridgexe2x80x9d disclosed in U.S. Pat. No. 5,000,687 is designed to enhance bridge strength by providing extensions (xe2x80x9cwingsxe2x80x9d) on the pontic which are adhered to the distal side of the abutment teeth. Woven fiber reinforcement of dental bridges is also disclosed in U.S. Pat. No. 4,728,291, U.S. Pat. No. 4,799,888 and U.S. Pat. No. 5,120,224, all to Golub; U.S. Pat. No. 5,098,304 to Scharf; and U.S. Pat. No. 5,176,951 to Rudo.
Other related devices that may use fiber-reinforced composites include splints, laminates, and veneers. Splints are used to provide strength and stability to loose teeth, or to temporary replacement teeth. Laminates and veneers may cover one or more teeth, and are used for aesthetic purposes. Fiber-reinforced splints, laminates, and veneers are described in the above-mentioned patents to Golub and Scharf.
While it is well known in the art to use a woven glass fabric as the fiber component of fiber-reinforced composites, a significant drawback has been the tendency of yarns of a woven and nonwoven glass fabric to fray, that is to separate from the fabric when the fabric is cut. Fraying of the yarns, especially at the ends of the cut fabric, presents difficulties in the processing and use of the fabric. Glass fabric is especially prone to fraying, which severely restricts its use. Accordingly, there remains a need for a glass fiber material that may be processed without fraying and separation of the fibers after the glass fiber fabric has been cut.
The above-described and other problems and deficiencies of the prior art are overcome or alleviated by the heat treated glass fiber material of the present invention, wherein the glass fiber material has been heat treated at a temperature less than or equal to the annealing temperature of the glass. The glass fiber material may be a uniform mesh, a random mesh, or a rope, tape or thread type material. Particularly preferred for use in the present invention is a woven glass fabric material. Heat treatment of the glass fiber material prior to cutting prevents fraying of the edges upon cutting, which greatly enhances ease of preparation of the fiber-reinforced restorations.